This invention pertains to a check rail lock for use with a double-hung window for drawing together the meeting rails of an upper and lower sash of the double-hung window, and locking the sash against opening movement. The check rail lock has a housing which mounts a rotatable cam for movement between locked and unlocked positions and which engages a keeper in a locked position. There is coacting structure for limiting movement of the cam to movement between locked and unlocked positions. A spring washer is rotatable with the cam and coacting detent structure on the spring washer and the housing releasably retains the cam in either locked or unlocked position.
A check rail lock of the general type disclosed herein is well known in the art. A housing mountable on one window sash has a rotatable cam therein for movement between locked and unlocked positions relative to a keeper mounted on the other sash and with a handle disposed exteriorly of the housing for rotating the cam. In a check rail lock of this type, it is also known to have structure for limiting the rotation of the cam and handle for movement between locked and unlocked positions of the cam and to have spring means for releasably retaining the cam in either locked or unlocked position.
The Bates U.S. Pat. No. 3,811,718 discloses a sash lock for double-hung windows wherein the handle and cam can rotate between a pair of stops fixed to a housing of the lock and a spring member supported by the housing functions to releasably hold the cam in either locked or unlocked position.
A check rail lock having an appearance generally similar to that disclosed herein is shown in the Anderson U.S. Pat. No. Des. 268,643.
A window lock having a cam with a square opening fitted to a shaft with a square section is shown in Chernosky, U.S. Pat. No. 4,436,328.
In order to manufacture and sell a check rail lock at the least possible cost, it is important to have the structure as simple as possible and require a minimal number of assembly steps. The invention disclosed herein is an improvement over the prior art in these respects.